I don't want to seem rude but if you don't know what clings are you don't know to much about stickers. Clings actually adhere to the glass, like a magnet so to speak without glue or any kind of adhesive and can be peeled off and reused again if needed. They normally are made to go on the inside of the glass but can also be made to go on the outside.
cheers
vern

No worries, I just do normal orcale vinyl stickers. Never done a cling type kind.